Perhaps you should try some spelling variations:
robert e » robert _, robert j
a robust » _ robust
gal » goal, gael, gail
heitmann » heinemann, hermann, hartmann
heitmannn » heinemannn, hermannn, hartmannn, heilmann
book » books, ebook
hermannn » hermann, hermawan
heimann » hermann, heinemann

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (( gal robert e. heitmann book ) OR ( a robust _. ((heitmannn OR hermannn) OR heimann) book ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( gal robert e. heitmann book ) or ( a robust _. ((heitmannn OR hermannn) or heimann) book ))~".
• Adding a wildcard symbol may retrieve word variants: (( gal robert e. heitmann book ) or ( a robust _. ((heitmannn OR hermannn) or heimann) book ))*.